The influenza virus constantly changes the proteins on its surface to adapt against vaccines, which is why a new formula of the flu vaccine must be developed every year. But the material on the inside of the virus is common to many strains of the flu, so vaccine researchers believe targeting the core of the virus could lead to a universal vaccine, researchers said. They tested this theory using the 2009 swine flu virus — and it worked, prompting researchers to announce they now have a "blueprint" for a new flu shot.

As the flu causes more than 200,000 hospitalizations and more than 30,000 deaths in the United States every year, medical experts across the board recommend that anyone older than 6 months get vaccinated. Pregnant women should also receive the vaccination, William Schaffner, MD, the chairman of the department of preventive medicine and professor of infectious diseases at the Vanderbilt University School of Medicine in Nashville, Tenn. told Weather.com, as it helps protect the baby during the first six months of life.

"The vaccine is the most effective way to prevent influenza each and every year," he said. "In patients where it doesn't prevent influenza completely, it contributes to preventing pneumonia, hospitalization and death. In other words, it makes a more serious illnesses milder, and that's very, very important."

This year's flu vaccine is now widely available through healthcare providers, including pharmacists.